Slurry agitator mechanism



March 12, 1963 R J CLAUSS ETAL 3,081,239

SLURRY AGITATOR MECHANISM Filed July 13, 1961 2 Sheets-Sheet l March 12, 1963 R. J. CLAUSS ETAL 3,081,239

SLURRY AGITATOR MECHANISM Filed July 13. 1961 2 Sheets-Sheet 2 KY\ Y INVHVTORJ. 77767;; J, 'Zaz/as. Way M lie? United States Patent Office 7 Patented Mar. 12, 1963 3,081,239 SLURRY AGITATOR MECHANISM Richard J. Clauss, Allen Park, Roy Walter Klein, St. Clair, and Leon J. Pianowski, Detroit, Mich., assignors, by mesne assignments, to The Udylite Corporation, Detroit, Mich., a corporation of Delaware Filed July 13, 1961, Ser. No. 123,719 4 Claims. (Cl. 204-49) The present invention broadly relates to agitating means and more particularly to an improved apparatus and method for maintaining a substantially uniform distribution of extremely fine-sized insoluble particles in a liquid slurry.

There are a large number of commercial processes which employ slurries comprising a liquid incorporating therein fine-sized insoluble particles distributed therethrough which, due to the tendency of the particles to settle to the bottom of a receptacle, necessitates agitation of the slurry to maintain a substantially uniform distribution of the particles and prevent stratification of the slurry.

A variety of mechanical agitation equipment has heretofore been employed or proposed for use to continuously agitate a slurry but which agitation means have alternately been ineffective .to prevent a Stratification and substantial degree of settling of the suspended particles therein or have created excessive turbulence hindering the use of the slurry for its intended purpose.

It is accordingly a primary object of the present invention to provide an improved apparatus and method for creating and maintaining a substantially uniform distribution of extremely fine-sized insoluble particles distributed throughout a liquid medium and which apparatus and method overcomes the problems presented by mechanical agitation means heretofore known.

Another object of the present invention is to provide an improved air agitation mechanism and method for introducing :a controlled quantity and distribution of a gas at the bottom of a liquid receptacle or tank which through the action of the upwardly rising bubbles through the body of the slurry effects a'controlled degree of agitation preventing settling of the fine-sized particles in the liquid and maintaining a substantially uniform distribution thereof.

Still another object of the present invention is to provide an improved air agitation mechanism and method for creating substantially uniform slurries of extremely fine-sized particles in .a liquid and which apparatus and method are of simple design, durable operation, simple control, and of economical manufacture and operation.

The foregoing and other objects of the present inven tion are achieved by immersing a conduit network in a liquid tank or receptacle contiguous to the bottom thereof and which network incorporates fine-sized apertures therealong at controlled intervals for emitting an upwardly rising stream of gaseous bubbles through the liquid effecting a desired degree of agitation of the slurry thereby preventing settling of the extremely fine-sized particles distributed therein and concurrently maintaining a substantially uniform distribution thereof throughout the liquid Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side elevation view of a typical liquid treating receptacle shown in section incorporating therein a conduit network disposed contiguous to the bottom thereof for introducing a controlled stream of gaseous bubbles at the bottom of the slurry contained therein effecting the desired degree of agitation thereof;

FIG. 2 is a vertical transverse sectional view of the liquid treating receptacle and air agitation system shown in FIGURE 1 and taken substantiallyalong the line 22 thereof;

FIG. 3 is a horizontal sectional view of the treating receptacle and conduit network shown in FIGURE 1 and taken substantially along the line 33 thereof, and

FIG. 4 is a transverse vertical sectional view through one of the distribution tubes of the conduit network shown in FIG. 3 and taken along the line 44 thereof.

The air agitation system and method comprising the present invention as shown in the accompanying drawings are particularly applicable for creating and maintaining a substantially uniform distribution of extremely fine-sized particles in bright and semi-bright aqueous acidic nickel plating solutions for producing satin-like fine-grained lustrous nickel platings on metallic base metals and which nickel plating has substantially improved corrosion resistance over satin-like nickel plated finishes heretofore known. Aqueous acidic nickel baths employed for producing a satin-like nickel finish can comprise a conventional Watts type bright or semibright nickel bath at a pH ranging from about 2 up to about 6 and including soluble nickel salts such as nickel sulfate, nickel chloride, nickel sulfamate, and the like, for example, and conventional brighteners of the types well known in the art in addition to from about 10 grams to about 500 grams per liter of substantially insoluble extremely finesized particles which are wetted by the liquid and of a particle size of less than about 5 microns and preferably less than 2 microns approaching colloidal dimensions.

The foregoing nickel plating slurry is representative of one typical use of the apparatus and method comprising the present invention. The necessity in this typical instance, of maintaining a substantially uniform distribution of the extremely fine-sizedinsoluble particles in the nickel plating slurry is evidenced by the uniformity of the satinlike lustrous finish of the electrodeposited nickel coating on the base metal. Variations in the degree of settling of the particles to the bottom of the tank which occurs with mechanical agitation apparatus of the type heretofore known, causes a continuous variation in the concentration of the suspended particles in the electroplating bath resulting in continuous variations in the surface finish obtained. The method and apparatus comprising the present invention also obviates in most instances the necessity of adding surface active agents to the nickel bath and provides for satin-like nickel finishes having a superior sheen and appearance. In accordance with the apparatus and method of agitating the bath as herein described, the quantity of settled particles in the bottom of the tank is minimized and the distribution thereof throughout the volume of liquid is maintained substantially uniform so that substantially the same satin-like finish is deposited on successive workpieces.

The suspended particles which can be employed for forming the aqueous slurry can comprise any one of a number of substantially insoluble particles which are wetted by the bath or liquid in which they are suspended and which include certain sulfates, carbonates, phosphates, oxalates, silicates, metallic oxides, carbides, silicides, nitrides, fluorides, and sulfides of a variety of metals ineluding aluminum, magnesium, boron, calcium, strontium,

barium, alkali metal earths, titanium, manganese, zirconium, iron, chromium, and the like. Insoluble particles which have been found particularly satisfactory for inclusion; in the aforementioned satin-like nickelplating bath include insoluble silicates of aluminum, magnesium, boron, calcium, strontium and barium, and mixed silicates of these metals, as well as certain sulfates, carbonates, phosphates and oxalates of alkaline earth metals, barium,

strontium, and calcium, as well as certain oxides, carbides,

silicides, nitrides, fluorides, and sulfides of the group consisting of silicon carbide, boron carbide, titanium carbide, silicon dioxide, manganese oxide, titanium oxide, zirconium oxide, aluminum oxide, ferric oxide, chromic oxide, boron nitride, calcium fluoride, strontium fluoride, barium fluoride, zinc sulfide, cadmium sulfide, and iron silicide. Of the foregoing kaolin (china clay) which is hydrous aluminum silicate is particularly satisfactory and finely powdered glass can also be satisfactorily employed in sizes less than about microns.

The agitation apparatus and method comprising the present invention is applicable to slurries having particles suspended therein in a concentration ranging from about grams per liter up to about 500 grams per liter and which particles are of the compositions hereinbefore set forth and of a particle size less than about 5 microns and preferably less than about 2 microns and approaching colloidal dimensions. In order tomaintain a substantially uniform distribution of the insoluble particles in the liquid avoiding any Stratification thereof in the bath, the distribution of the gaseous stream of bubbles must be controlled within the limits subsequently to be described in order to achieve the benefits of the present invention.

A typical liquid treating receptacle or tank 10 is illustrated in the drawings which is provided with a conduit network or distribution coil 12 disposed contiguous to the bottom thereof and from which any suitable gas which is compatible with the slurry, such as air, for example, is introduced creating the desired degree of agitation of the slurry. The tank 10 can also be provided with a suitable heating coil 14 immersed therein for maintaining the slurry within a controlled temperature range. A suitable blower system generally indicated at 16 comprising a motor 18 and a pressure blower 20 drivingly connected thereto is mounted adjacent to the tank 10 and supported on a frame 21 connected to the side partition of the tank. The pressure blower 20 may comprise any suitable blower capable of supplying a gas that the requisite pressure and capacity consistent with the size of the conduit network and the depth thereof beneath the surface of the slurry in which it is immersed.

The pressure blower 20 is provided with an inlet tube 22 and a discharge tube 24 which is connected to a vertical header 26 of the distributor coil 12 as is best shown in FIGURE 1. It will be appreciated that in lieu of the blower system 16 as shown in the drawings, which is a self-contained unit disposed adjacent to the tank 10, a pressurized gas can also satisfactorily be supplied to the distribution coil 12 by a suitable main pressure header connected to the distribution coils of each of a series of the tanks 10.

The distribution coil 12 as shown in the drawings, comprises a main supply line or manifold 28 of an L-shaped configuration including the vertical header 26 and a horizontal portion or horizontal header 30 disposed adjacent to the bottom of the tank and extending for substantially the entire width thereof. A plurality of distribution tubes 32 are connected and disposed in communication with the interior of the horizontal header 30 and extend therefrom in substantially parallel longitudinally spaced intervals and positioned slightly above the tank bottom. The ends of each of the distribution tubes 32 are closed by a suitable cap 34 which is preferably of a diameter greater than the diameter of the distribution tubes so as to support the ends thereof on the tank bottom and maintain the distribution tubes 32 at a substantially uniformly spaced distance from the bottom surface of the tank 10.

Because of the buoyancy of the distribution coil 12 during operation, the distribution coil is anchored or otherwise secured to the bottom partition of the tank and preferably is provided with a series of notched counterweights 36 extending transversely of the distribution tubes of a total weight sutficient to prevent pulsation or other movement of the distribution coil during use. Each of the distribution tubes 32 are provided with a plurality of apertures or discharge nozzles 38 through which the gas, such as air, is discharged adjacent to the bottom of the tank. The discharge nozzles 38 are arranged in a pair of parallel rows along the underside of the distribution tubes 32 as can be best seen in FIG. 4. The axis of each of the discharge nozzles is directed downwardly toward the bottom of the tank and the angular inclination thereof from the vertical can range from about 15 to about 60, and preferably from about 40 to about 50. By this arrange ment the gas discharged through the discharge nozzles 38 is directed downwardly against the bottom surface of the tank 10 sweeping away any particles which may have settled thereon and thereafter the bubbles rise upwardly through the slurry creating an upwardly directed turbulence to overcome the settling tendency of the extremely fine-sized insoluble particles distributed therethrough. In the specific arrangement shown in FIG. 4, the rows of the discharge nozzles 38 are disposed along the circumference of the distributor tube 32 at an arcuate increment of about 45 from the vertical.

The discharge nozzles 38 in the pairs of rows along the bottom side of each of the distribution tubes 32 are longitudinally offset from the apertures or discharge nozzles in the row adjacent thereto a distance corresponding to about one-half the spacing of the discharge nozzles therealong. It is preferred that the spacing of the discharged nozzles and the offset arrangement thereof be substantially identical for each of the distribution tubes 32 of the distribution coil 12 providing therewith an airflow pattern as schematically indicated in FIG. 3 by the arrows.

In order to achieve the desired degree of agitation of the slurry to maintain concentrations ranging from about 10 grams up to about 500 grams of the particles having a size less than about 5 microns and of the composition hereinbefore described in a substantially uniform distribution throughout the liquid, it is necessary that the relative spacing of the distribution tubes 32 and the size and spacing of the discharge nozzles 38 therealong be controlled within a selected range. It has been found that in order to achieve the desired degree of agitation, the discharge nozzles 38 can range in diameter from about inch, up to about &6; inch, and preferably about inch, and the rectangular spacing of the discharge nozzles in accordance with the pattern shown in FIG. 3 should not exceed 8 inches between adjacent discharge nozzles and preferably a spacing ranging from about 5 inches to 7 inches, so as to provide a nozzle distribution density of from about 3 to about 6 nozzles per square foot of tank area. At this spacing interval, the introduction of a gas through the discharge nozzles at a pressure ranging from about 1 to about 2 p.s.i., and preferably about 1 /2 p.s.i., above the hydrostatic pressure at the outside of the discharge nozzle of the distribution coil results in a gas flow rate of about .35 to about .6, and preferably of from about .45 to about .55, cubic feet per minute (c.f.m.) of gas per nozzle measured at the hydrostatic pressure of the slurry at that point and a substantially uniform distribution of the upwardly rising bubbles through the slurry maintaining the insoluble particles therein substantially uniformly distributed throughout. This condition is equivalent to effecting an upward flow rate of gas of from about 1 to about 3.5 c.f.m. per square foot of tank area at the level of the distribution coil, and preferably from about 1.3 to about 3.0 c.f.m. The diameter of the discharge nozzles can vary within the range set forth above. Nozzles having a diameter less than about of an inch are susceptible to plugging whereas nozzle sizes in excess of about of an inch produce excessively large size bubbles which provide an undesired degree of agitation and in the case of satin-like nickel baths are particularly objectionable because of their tendency to contact the surfaces of workpieces therein, causing non-uniform satin-like nickel finishes.

The positioning of the discharge nozzles 38 along the underside of the distribution tubes 32 also prevents plugging of the nozzles and facilitates purging of the interior thereof during startup of the distribution coil. For example, when the distribution coil immersed in the slurry is shut down by stopping the flow of pressurized gas therethrough, the interior of the distribution coil fills with the liquid and suspended particles therein up to a point corresponding to the level of the slurry in the tank 10. In addition, in the absence of agitation, the suspended particles settle to the bottom of the tank and frequently completely bury the distribution coil. On startup of the blower system 16, the initial pressurized air first serves to purge the interior of the distribution coil of the liquid therein and additionally sweeps any of the finely divided particles out through the discharge nozzles 38. The discharge of the purged slurry through the discharge nozzles followed thereafter by the discharge of the pressurized gas serve-s to agitate and dislodge the thick layer of settled particles along the bottom of the tank 10 and the rising stream of air bubbles lifts the particles upwardly toward the upper surface of the liquid. The impingement of the air discharged through the discharge nozzles 38 against the bottom surface of the tank eventually serves to sweep substantially all of the settled particle-s therefrom and distribute them substantially uniformly throughout the liquid. After a period of time the slurry attains a degree of uniformity after which it can be used for processing in accordance with the specific operation being performed. To reduce the period of time necessary to achieve a substantially uniform distribution of the suspended particles after they have been allowed to completely settle to the bottom of the tank, a higher pressure of the agitation gas can be employed during the startup phase to facilitate fragmentation and agitation of the settled sludge of particles after which the pressure is reduced to the range hereinbefore described for maintaining a mild degree of agitation and inhibiting settling and Stratification of the particles in the slurry.

The foregoing parameters also apply to tank bottoms which are not horizontal as shown in the drawings but which may be of a concave or trough-like configuration. In such event, the distribution tubes of the conduit network should be disposed contiguous to and substantially follow the contour of the tank bottom and a projection of the discharge apertures therealong on a horizontal plane should conform to the rectangular spacing pattern of not greater than 8 inches and preferably between about and 7 inches between adjacent discharge nozzles or from about 3 to about 6 nozzles per square foot of tank area in accordance with that hereinbefore described. The specific spacing arrangement, angularity of the discharge nozzles, and differential pressure of the gas discharged therethrough can be varied within the ranges hereinbefore set forth depending on such related factors as the concentration, size, and density of the insoluble particles suspended in the liquid; the viscosity and specific gravity of the liquid in which the particles are suspended; and the temperature of the gas and slurry in order to achieve a uniform distribution and desired degree of turbulence in V the slurry.

The materials from which the conduit network 12 is comprised is not critical provided that if materials susceptible to corrosive attack by alkaline or acidic slurries are used, such as steel, for example, the surfaces of the conduit network should be provided with a protective coating such as a plastic coating of polyvinyl chloride, for example. Similarly, the counterweights 36 should be provided with a protective coating to prevent corrosive attack thereof. The distribution network can also be made of non-corrosive materials such as stainless steels, for example, or suitable high strength plastic materials which are not affected by the acidity or alkalinity of heated slurry solutions, such as, for example, phenolic plastic or polyvinyl chloride plastic tubing.

While it will be apparent that the preferred embodi- Ms.. ments herein illustrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope of fair meaning of the subjoined claims.

What is claimed is:

l. A satin-like nickel electroplating agitator mechanism adapted to be disposed in a tank for agitating an electroplating slurry contained therein incorporating from 10 grams up to 500 grams per liter of insoluble particles having a size predominantly less than 5 microns distributed throughout, comprising a manifold at least a portion of which is immersed in the slurry, a plurality of distribution conduits connected to said manifold disposed in communication with the interior thereof and extending therefrom contiguous to and over substantially the entire bottom surface of the tank, each of said distribution conduits provided with a plurality of downwardly directed nozzles therein inclined at an angle of from 40 to 50 from the vertical and arranged at substantially equally spaced intervals providing a concentration ranging from 3 to 6 of said noozles per square foot of tank area, and supply means for supplying a pressurized gas to said manifold and said distribution conduits connected thereto at a pressure to effect a discharge of said gas from each of said nozzles at a rate ranging from .45 to .55 cubic feet per minute at the outlet of said noozles.

2. In a satin-like nickel electroplating apparatus, the combination comprising a tank, a nickel plating slurry in said tank including an extremely fine sized insoluble particulated solids content distributed therethrough ranging in concentration from 10 grams to 500 grams per liter and having a particle size predominantly less than 5 microns, an agitation mechanism including conduit means immersed in said tank and disposed contiguous to and extending over substantially the entire botom thereof, said conduit means including a plurality of downwardly directed nozzles therein inclined at an angle of from 15 to 60 from the vertical and having a diameter ranging from to of an inch, said nozzles disposed at intervals measured in a horizontal plane ranging from 5 inches to 8 inches from adjacent ones of said nozzles and means for supplying a pressurized gas to said conduit means at a differential pressure of from 1 to 2 psi at the outlet of said nozzles above the hydrostatic head of said slurry effecting a gaseous sweeping of the bottom of said tank and agitation of said slurry for maintaining a substantially uniform distribution of said particles therethrough.

3. The method of agitating a satin-like nickel electroplating slurry containing from 10 grams to 500 grams of insoluble particles therein having a particle size predominantly less than 5 microns comprising the step of directing a plurality of pressurized streams of gas down- WaIdly so as to impinge against the bottom of a tank containing the slurry at an angularity ranging from 15 to 60 from the vertical and at an average cross sectional flow rate measured at the bottom of the tank ranging from 1 to 3.5 cubic feet per minute per square foot of tank area, said streams of gas positioned in substantially uniform pattern over substantially the entire bottom of the tank at a frequency ranging from 3 to 6 of said streams of gas per square foot of tank area.

4. The method of agitating a satin li ke nickel electroplating bath incorporating therein from 10 grams to 500 grams per liter of insoluble particles having a particle size predominantly less than 5 microns comprising the step of directing a plurality of pressurized streams of gas downwardly so as to impinge against the bottom of a tank containing the slurry and at an angularity ranging from 40 to 50 from the vertical and at an average cross sectional flow rate ranging from 1.3 to 3.0 cubic feet per minute per square foot of tank area measured at the bottom thereof, said streams of gas positioned in a substantially uniform pattern over substantially the entire cross sectional area of the tank at a frequency ranging from 3 to 6 of said streams of gas per square foot of tank area.

References Cited in the file of this patent UNITED STATES PATENTS 8 Tietig Sept. 4, 1945 Hakes Feb. 22, 1955 Zavod Jan. 10, 1956 Wirts Dec. 18, 1956 Schroeder May 6, 1958 FOREIGN PATENTS Austr-ia Apr. 25, 1930 France Nov. 10, 1953 

3. THE METHOD OF AGITATING A SATIN-LIKE NICKEL ELECTROPLATING SLURRY CONTAINING FROM 10 GRAMS TO 500 GRMAS OF INSOLUBLE PARTICLES THEREIN HAVING A PARTICLES SIZE PREDOMINANTLY LESS THAN 5 MICRONS COMPRISING THE STEP OF DIRECTING A PLURALITY OF PRESSURIZED STREAMS OF GAS DOWNWARDLY SO AS TO IMPINGE AGAINST THE BOTTOM OF A TANK CONTAINING THE SLURRY AT AN ANGULARITY RANGING FROM 15* TO 60* FROM THE VERTICAL AND AT AN AVERAGE CROSS SECTIONAL FLOW RATE MEASURED AT THE BOTTOM OF THE TANK RANGING FROM 1 TO 3.5 CUBIC FEET PER MINUTE PER SQUARE FOOT OF TANK AREA, SAID STREAMS OF GAS POSITIONED IN SUBSTANTIALLY UNIFORM PATTERN OVER SUBSTANTIALLY THE ENTIRE BOTTOM OF THE TANK AT A FREQUENCY RANGING FROM 3 TO 6 OF SAID STREAMS OF GAS PER SQUARE FOOT OF TANK AREA. 